This message was posted on behalf of Intel Corporation
Since you are getting a 1-5-4-2 beep sequence, which indicates a power fault or failure try to resolve this issue by following these steps:
-Remove and reinsert the power supply or power supplies.
-If your system supports dual or redundant power supplies, start up your computer using a single power supply.
-Update the motherboard system firmware to the latest version.
-Try a higher wattage power supply.
Please confirm the System Status Indicator LED color in order for us to provide further troubleshooting steps.
I found the issue.
The jumper J1E2 was silmply not set properly. The jumper was turned 90° so it made contact with only one pin. I fixed that and now the board works absolutely fine.
Thank you very much anyways!
Greetings from Germany